Rewar S, Bansal B K, Singh C J
Abstract
Ocular drug delivery is the most fascinating and challenging task faced by pharmaceutical researchers. Conventional dosage forms such as eye drops are the most used dosage form by ocular route, in spite of their low bioavailability and the pulsed release of the drug where it is expected that direct application of the drug to the eye will give maximum response; however after instillation of an eye drop, about 70% of the administered volume can be seen to be lost by different factors. For this reason new ocular drug delivery vehicles have been developed in order to minimize the amount of the drug lost from the eye and at the same time provide maximum response with reduced frequency of administration. Transport of drugs applied by traditional dosage forms is restricted to the eye, and therapeutic drug concentrations in the target tissues are not maintained for a long duration since the eyes are protected by a unique anatomy and physiology. Major problems encountered by conventional ocular dosage forms include rapid pre-corneal drug loss due to naso-lacrimal drainage; tear turnover and drug dilution resulting in poor bio-availability. Therefore, efforts to improve ocular drug bio-availability led to development of novel drug delivery dosage forms such as nano particles, liposomes, hydrogels, ocuserts and muco-adhesive formulations.